A typical burner for combustion apparatus in metal heating furnaces, ceramic furnaces and the like most extensively used is of the air atomizing type in which fuel is atomized by the flow of high speed air to burn a group of thus atomized substances. The performance of such a burner is decided by the atomization performance and combustion performance of the fuel. If the atomization performance is poor, the particles of fuel become large, failing to complete burning within a predetermined period of time and as a result, soot and smoke may sometimes result.
In addition, in order to burn the group of particles poorly atomized as described above, a large quantity of excess air is required to worsen the thermal efficiency, as a consequence of which the fuel is not only consumed wastefully but material to be heated in the combustion apparatus is sometimes contaminated.
In general, the atomization performance of the air atomizing type burner is decided by the ratio Qa/Qb between the air flow rate Qa (m.sup.3 hr) and the amount of fuel consumption Qb (m.sup.3 /hr). If this ratio is small, the atomization performance is poor, and if the ratio is large, say, 2.times.10.sup.3, Sauter's mean diameter d.sub.32 (=Znd.sup.3 /Znd.sup.2) of body area of the group of particles is made constant. It will be noted that the value of the ratio is about twenty percent of the theoretical amount of air required for combustion. The greater the relative speed (Ua-Ub) between the air speed Ua (m/sec) for atomization (which is decided by pressure of a blower) and the linear speed Ub (m/sec) of fuel forced out of a nozzle orifice, the smaller will be Sauter's mean diameter d.sub.32. Hence, the atomization performance is decided extremely close to the nozzle outlet where gas and air come into contact.
In prior art atomizing type burners, the injecting direction of fuel is parallel to the direction of air flow.
In the burners in which the injecting direction of fuel is parallel to the direction of air flow as mentioned above, liquid hole-diameter must be reduced to about 1-2 mm in order to enhance the atomization performance. Therefore, a limit in the amount of fuel consumption is 10 to 20 l/hr. In burners of large capacity more than 100 l/hr, the liquid hole-diameter must be made large and hence, the atomization performance is naturally decreased. Also, in order to increase the capacity of the burner, a multi-hole type burner of small liquid hole-diameter is employed. In this type of burner, however, contact between gas and liquid is bad and it is not possible to expect atomized disintegration of the fuel.
The present invention overcomes the disadvantages noted above with respect to prior art devices. That is, in accordance with the burner for combustion apparatus of the present invention, the tip of the nozzle is blocked, an outer peripheral surface has an inclined portion inclined upstream of the air flow, fuel is forced in a string-like pattern through a multiplicity of outflow passageways formed on the inclined portion while at the same time the flow of air is substantially brought to intersect thereto at right angles to disintegrate the fuel in an atomized pattern. The fuel flowing along the inclined portion is formed into substances in the form of film and subject to filmed disintegration at the top of a frusto-conical portion.
That is, in accordance with the present burner, the fuel to be burned impinges upon air and flows along the inclined portion to be formed into a film-like pattern so that even if pressure of the air for atomizing fuel is decreased, the fuel may be atomized into a group of extremely fine particles. Thus, the present invention possesses an advantage that the burning performance may be enhanced. Moreover, the provision of plural stages of the frustoconical portions cause the fuel formed into a film-like pattern to repeat the atomization phenomenon and the fuel impinges upon air, which leads to the employment of the so-called "multistage atomization system". In this manner, atomization of fuel is further promoted, which constitutes another advantage of the invention.